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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.

prepared by Antonio J
tographs taken by Agric
in Feb. 8, 1964. Water
C. Bridges and W.E. K
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HYDROLOGIC SETTING OF DEER POINT LAKE
NEAR PANAMA CITY, FLORIDA
By G. H. Hughes
ABSTRACT
Deer Point Lake is a much more dynamic water body than is
apparent to those who view the lake only casually. The lake level and
the temperature of the lake water, for example, vary almost
continually within limits of a few feet for the lake level and several
degrees for the temperature. The chemical quality of the lake water
also varies significantly. Some of these variations are partly
documented by data collected in past years; however, useful
evaluations of these data require some understanding of the relations
and inter-relations that exist among the many variables involved. This
report compiles much of the hydrologic data that pertain to Deer
Point Lake and examines the significance of the data in light of some
of the hydrologic principles that apply.
INTRODUCTION
Deer Point Lake was formed in 1961 by construction of a
low-head causeway dam across the northern part of North Bay at
Deer Point about 8 miles north of Panama City, I la. See figure 1.
The lake provides an ample water supply for the continued economic
growth of the Panama City area and adds to the water-oriented
recreational facilities available for tourists and residents of that area.
The purpose of this report is to compile much of the hydrologic
data that pertain to Deer Poinmt Lake and to cast the data in a
meaningful light by relating it to some of the hydrologic principles
that apply. The report serves to demonstrate the broad
understanding of hydrologic problems required of public officials
and other interested parties who arc concerned with the wise use of
the natural resources of the Panama City area.
Deer Point Lake dam impounds part of the flow of four
creeks-Econfina, Bear, Bayou George, and Big Cedar. The remainder
of the flow spills into North Bay. Deer Point Lake covers about
4,700 acres and stores about 32,000 acre-feet of water at spillway
level of the dam. 4.5 feet (elevations here given as feet above mean
sea level). About half the area of the lake is made up of open-water
areas that were formerly part of North Bay and the inlet to Bayou
George Creek. The rest of the lake area extends inland into Econfina
Creek, Bear Creek, and Big Cedar Creek drainage basins, where the
water is generally shallow and densely filled with aquatic vegetation.
Impoundment of fresh water in Deer Point Lake began with
closing of the causeway dam on November 17, 1961. Water began
spilling over the dam on November 28, 1961, and stabilized at a level
of about 5.0 feet on December 2, 1961. Since that time the lake level
has ranged from a maximum of 6.38 feet on September 29, 1963, to
a minimum of 4.82 feet on October 14. 1968. Water is from 8 to 16
feet deep in most open-water areas-with the lake at its usual level of
about 5.0 feet-and is deepest in the center of the lake near the dam.
Small pockets of deep water are found along former stream channels
now covered by the lake.
LAKE-LEVEL FLUCTUATIONS
The level of Deer Point Lake varies with the volume of streamflow
passing through the lake, as is evident from the similarity of the
streamiflow and lake-level variations portrayed by graphs in figure 2.
The streamflow variations of Bayou George Creek and Big Cedar
Creek are similar to those of Econfina Creek and Bear Creek;
however. Bayou George Creek and Big Cedar Creek contribute only
about 6 percent of the total streamflow passing through the lake, so
these creeks affect the lake level only slightly. Table 1 gives the
proportion of streamflow that enters the lake from each of the four
creeks for two conditions-average flow and low flow. The
average-flow data correspond approximately to the flow that
occurred in 1966 (fig. 2), whereas the low-flow data correspond to a
drought such as occurred in 1968.
During 1968 the total water withdrawn from Deer Point Lake for
municipal and industrial use averaged about 40 mgd (million gallons
per day), or slightly less than 15 percent of the streamflow that
entered the lake during the crux of the 1968 drought. Thus, as long
as the streamflow is undiminished by upstream developments, the
lake and stream system provides a dependable supply of water for
appreciable expansion of use in the Panama City area.
Streamflow that enters Deer Point Lake results from rainfall on
the drainage basins of the several creeks involved. Consequently, the
streamflow varies with rainfall. Variations of the yearly rainfall
recorded at Panama City-shown in figure 3-generally apply to
nearby inland areas and, hence, to the streamflow passing through
Deer Point Lake.
iThe yearly rainfall recorded at Panama City since 1898 has
averaged 58 inches; but it has varied greatly, from a minimum of
slightly less than 37 inches in 1917 to a maximum of slightly more
than 85 inches in 1959. Although such extreme variations are
unusual, yearly rainfalls greater than 70 inches were recorded several
times, and the minimum yearly rainfall of record was almost equaled
in 1931. 1938, and 1968.
The flow of I confina Creek has been measured since 1936 at the
U. S. Geological Survey's gaging station, Econfina Creek near
Bennett, I la.. about 2 miles upstream from Deer Point Lake. See
figure 4. The variations in the yearly streamflow generally reflect the
variations in rainfall at Panama City.
Because of the relative lack of rainfall in 1967-68, the flow of
L:confina Creek gradually declined to a minimum of 210-215 mrgd
during September and October 1968. During these months Deer
Point Lake remained within a few hundredths of a foot of its
minimum level of record-4.82 feet on October 14, 1968.
The recorded minimum flow of lconfma Creek near Bennett was
198 mgd on January 9, 1956--a result of the 1954-56 drought.
Correlation studies of the flow of Lconfina Creek and the level of
Deer Point Lake indicate that a change in the inflow to the lake
corresponding to a change in lthe low of Econfina Creek from
210-215 mgd to 198 mgd would cause only slight decline of the lake
level-probably less than 0.05 leet.
According to Pride and Crooks (1962). the 1954-56 drought was
the most severe drought suffered by the state of Florida since at least
1881. Analysis of the record of rainfall at Panama City indicates that
the Panama City area conformed to the statewide pattern. Based on
the assumption that the magnitude and distribution of past rainfalls
apply to future rainfalls, a drought as severe as the 1954-56 drought
probably will occur, on the average, only once in every 50-100 years.
Consequently, barring upstream developments that would decrease
streamflow, the frequency at which the flow of Econfina Creek
might decline significantly below 198 mgd should be about the same.
Keeping minind that streams of a given area follow the same flow
trends, particularly during dry periods, and that lconfina Creek is
the chief source of water for Deer Point Lake during dry periods, and
barring changes in critical features of Deer Point Lake dam and large
increases of water withdrawals from the lake, it therefore follows
that, on the average, Deer Point Lake probably will decline
significantly below 4.8 feet only once in every 50-100 years. Note
that if withdrawals of lake water are greatly increased over present
withdrawals, however, the lake level may decline more frequently
below a level of 4.8 feet during drought periods less severe than lhe
1954-56 drought.
Deer Point Lake rose to a maximum observed level of 6.38 feet on
September 29, 1963, but also reached a level of 6.30 feet twice in
1964, a level of 6.20 feet in 1965. and a level of 6.28 feet in 1966
(U. S. Geological Survey, 1963-66). Thus, the 1963 flood level seems
not to represent an outstanding flood.
The rainstorm that produced the 1963 flood level of 6.38 feet at
Deer Point Lake caused a flood flow of 847 mgd at Econfina Creek
near Bennett (U. S. Geological Survey. 1963); however, a maximum
flood flow of 3,140 mgd was recorded at Econfina Creek near
Bennett on April 2, 1948 (U. S. Geological Survey, 1951). Assuming
that the rainfall distribution of the 1963 storm vould apply and that
the flood flow over Deer Point Lake dam varies directly with the
flood flow of Econfina Creek near Bennett, simple computations
indicate that a recurrence of the 1948 flood would raise the level of
Deer Point Lake to about 9 feet.
In a study of floods in the region including Econfina Creek, Barnes
and Golden (1962, p. 42) concluded that the 1948 flood flow of
Econfina Creek near Bennett had a recurrence interval greater than
50 years. On this basis, therefore, the probability is less than 2
percent that Deer Point Lake will rise in any one year to a level of 9
feet.
ORIGIN OF THE LAKE WATER
Streamflow that enters Deer Point Lake is derived from rainfall by
two different hydrologic routes. Part of the streamflow is runoff that
results from the overland flow of rainfall into stream channels.
Overland flow occurs only during and immediately after rainstorms,
commonly producing relatively high rates of runoff for relatively
short periods of time. The abrupt rises in level of Deer Point Lake
(fig. 2) are due primarily to runoff.
Rainfall that does not flow directly from the land surface into
stream channels is absorbed by surficial materials or is temporarily
stored in land-surface depressions. Part of the rainfall subsequently
evaporates from the land and water surfaces, or is transpired by
plants, but part of it percolates downward to the water table. In the
creek basins that supply streamflow to Deer Point Lake, the surficial
materials are generally permeable sands of variable but appreciable
thickness that readily absorb rainfall and transmit it to the water
table.
According to Musgrove, Foster, and Toler (1965, p.5), however,
"The sands of the water-table aquifer cover a relatively impermeable
layer of sandy clay and clayey shell material which forms an
aquiclude (a formation that confines water to aquifers above and
below it) between the water-table aquifer and the artesian aquifers
below.... This aquiclude is present throughout the basin except where
it has been breached by collapse into solution chambers or by
erosion along Econfina Creek." The aquiclude generally restricts the
downward movement of water min the surficial material and causes
most of the rainfall that reaches the water table to emerge in the
stream channels.

TABLE 2. CHEMICAL ANALYSES OF WATER IN DEER POINT LAKE AND SELECTED
TRIBUTARY STREAMS (CHEMICAL CONSTITUENTS IN MILLIGRAMS PER LITER)

3- d

5-24-66 S5.18 1.0 0.10 8.0 2.2

8-18-66 S5.29 38

2-24-67 S 5.10 3.9

.20 4.4 1.0

.21 6.3 1.4

5- 9-67 S4.96 2.1 .02 10

6- 6-68 S4.92 1.3 .10 12

5-12-67 Q406 5.2

.00 15 2.1

is 7 7 u

I, I .- l

Figure 1. Map of Deer Point Lake and tributary streams.

Creek basin

The aquiclude overlies extensive formations of limestone generally
known as the Floridan aquifer. In most of Bay County the aquiclude
is so impermeable that it prevents any appreciable natural exchange
of water between the Floridan aquifer and the water-table aquifer or
thie streams. In the southern part of Washington County, however,
where the limestone of the Floriilan aquifer is at or near the land
surface, the aquiclude in some pla' es is missing and in other places is
present but is breached by sinkholes formed by the collapse of
overlying materials into solution cavities in the limestone. Here the
water from rainfall freely enters the lloridan aquifer.
The principal area where water enters the Floridan aquifer in tIhe
vicinity of Panama City is probably the Deadening Lake area-an area
riddled with sinkholes, some of which contain water to form ponds
or lakes but many of which are dry most of the time. The Deadening
Lake area is part of White Oak Cieck basin, a large closed drainage
basin that adjoins Econfina Creek basin. Rainfall on White Oak Creek
basin either evaporates or enter, the Floridan aquifer, primarily
through sinkhole connections in the Deadening Lake area. Because
Econfina Creek in places has eroded through the aquiclude that
generally confines water under ,rtcesan pressure in the Floridan
aquifer, much of thle water that enters the Floridan aquifer in the
Deadening Lake area emerges as spring flow in Econfina Creek.
Musgrove, Foster, and Toler (1965, p.44) estimated that Econfina
Creek derives about two-thirds of its total flow from the Iloridan
aquifer. This added water account, for the gross disparity, especially
during dry periods, between the water yields of Bear Creek and
Econfina Creek basins (table F1, two adjacent drainage basins
approximately the same size and presumably receiving about the
same rainfall.
Thus, the ground-water components of streamflow, water from
the water-table and Floridan aquifers, sustain the level of Deer Point
Lake during rainless periods.
CHEMICAL CONSTITUENTS OF THE LAKE WATER
When the causeway-dam forming Deer Point Lake was closed.
water in the lake was extremely saline. Chemical analyses of water
taken from the lake the day before the dam was closed (Musgrove,
Foster, and Toler, 1968) indicate 'hat the concentration of chloride
averaged about 11,000 mg/l (milligrams per liter). This concentration
is slightly greater than half the concentration of chloride in ocean
water. Because of mixing of the saline lake water with the large
throughflow of fresh water, however, the average concentration of
chloride was reduced to less than 400 mg/l within 3 months after
dam closure and to less than 40 mg/1 within a year. The
concentration of chloride in the lake water presently varies slightly,
as indicated by the results of chemical analyses listed in table 2. but
generally remains less than 25 mg/I
Streamflow passing through Deer Point Lake is great enough, on
the average, to replace the stored lake water about twice each month.
Thus water generally does not remain in the lake long enough for
significant concentration of dissoled minerals by evaporation of the
lake water. Because of the rapid fieshening of the lake water during
the first year of the lake's existence, the present lake water might be
expected to be chemically the same as creek water mixed
proportionately according to the volume of streamflow from the
creeks involved. But such is not the case.
The chemical quality of water from the different streams that
enter Deer Point Lake has been described by Musgrove, Foster, and
Toler (1965, 1968). The waters of Bayou George Creek and Big
Cedar Creek are chemically about the same as the water of Bear
Creek, each containing small but like amounts of the same chemical
constituents. The water of Ecorfina Creek is substantially more
mineralized than the water of the other creeks because of the
calcium and magnesium carbonate acquired by that part of the
I confma Creek water that passes through the I loridan aquifer. Table
2 includes results of chemical analyses of water from Econfina Creek
and Bear Creek for times when comparable data are available for
Deer Point Lake.
In a blend of chemically different waters, the concentration of a
specific chemical constituent falls within the range of concentration
of the same constituent in the various waters involved. Thus, if Deer
Point Lake water is simply an unitered mixture of water from the
different tributaries, the concentration of its chemical constituents
must fall respectively between the concentrations of the same
constituents in the waters of Bear Creek and Econfina Creek.
The concentrations of calcium and bicarbonate in the lake water
do fall within the range of concentration of these two constituents in
the waters of Bear Creek and Ecoifina Creek, specifically indicating
a mixture of about three parts water from Econfina Creek to one
part water from the other creeks involved. The concentrations ol
chloride, sodium, sulfate, magnesium, and potassium, however, are
all significantly greater in Deer Poiat Lake water than in the water of
Econfina Creek or Bear Creek-a conditionn that cannot result from
simply mixing the creek waters.
Evaporation of the lake water cannot be the explanation of the
increased concentrations of chloride, sodium, sulfate, magnesium,
and potassium, because, in the range of concentrations involved,
evaporation would concentrate calcium and bicarbonate to the same
degree. Hence, the increased concentrations of chloride, sodium,
sulfate, magnesium, and potassium require the addition of these
minerals from some source other than streamflow. The relative
concentrations of the particular constituents involved strongly
suggest that ocean water is the source of the added minerals because
98 percent of the chemical constituents of ocean water are made up
of chloride (55 percent), sodium (31 percent), sulfate (7 percent),
r ,, .... ..1 i-. I potassium (1 percent) (Hem, 1959).
.Ir 1.1 .Ide, sodium, sulfate, magnesium, and
potassium in the lake water over that in a mixture of streamflow
cannot be attributed to ocean water in the lake at the time of dam
closure, because, allowing for the minerals since added by
streamflow, simple calculations show that more minerals have been
removed from the lake by water spilling over the dam than were
originally stored in the lake. Similarly, the increase of these minerals
cannot be attributed to the direct mixing of lake water with fresh
ocean water because the hydrostatic pressure differential maintained
by the dam precludes such mixing. The most probable source of such
minerals is sediments generally underlying the lake-sediments that
once were saturated with ocean water. The most likely agent for
inducting the minerals into the lake water is ground water passing
through the sediments as it enters the sides and bottom of the lake.
Ground water enters the lake directly from the water-table
aquifer, which is contiguous with the lake, and probably from the
Floridan aquifer, which underlies the lake at depth. The volume of
ground water that enters the lak,. directly is small relative to the
streamflow passing through the lake. But the ground water in passing
through the sediments impregnated with ocean water becomes highly
mineralized relative to the streamftow. Because the density of water
increases with increased mineral content, the highly mineralized
former ground water tends to remain on the lake bottom. Thus, a
detectable buildup of minerals occurs during prolonged periods of
low streamflow. The sparse data available indicate that intermittent
flood flows flush the accumulated minerals from the lake.
Although the chemical characteristic$ of Deer Point Lake water
are of some hydrologic significance, the concentrations of the several
different minerals are not high for natural lakes in Florida and, in
fact, are in each case well below the limiting concentrations
recommended for drinking water (U. S. Public Health Service, 1962).

TEMPERATURE VARIATIONS OF THE LAKE WATER
The temperature of water in Deer Point Lake has not been
measured well enough to define the temperature variations that
occur. However, some understanding of these variations in shallow
lakes in Florida can be gained from consideration of some of the
factors involved.
The temperature of water in open areas of a shallow lake, such as
Deer Point Lake, generally does not vary appreciably in an areal
sense, but it does vary diurnally and seasonally, and at times, it varies
appreciably with depth. Temperature variations of lake water
basically are due to variations in solar radiation incident to the lake
surface. When incident solar radiation follows an increasing trend, as
in the spring of the year, the lake temporarily receives more energy
from the sun than can be dissipated by radiation, conduction, and
evaporation. The lake water stores some of the available energy,
thereby increasing its temperature until equilibrium is attained. When
the trend of incident solar radiation is decreasing, as in the fall of the
year, the lake temporarily can dissipate more energy than is received
from the sun because the temperature of the lake water is higher
than necessary to maintain equilibrium. The lake water in this case
releases stored energy, with a consequent decrease in temperature of
the lake water. Hence, the temperature of the lake water increases
from winter to summer and decreases from summer to winter.
Similarly, the temperature of lake water varies daily, increasing
during the morning-until noon or mid-afternoon-and decreasing
during the evening.
The temperature variations of water in a shallow lake are similar to
and almost in phase with the temperature variations of the local air.
However, the diurnal temperature variation of lake water generally is
substantially less than that of air. For example, the temperature of
surface water of a lake commonly may vary diurnally about
10-12 F (degrees Fahrenheit) if the day is warm, sunny, and calm.
Under i.. i.: J, -. the temperature of the local air may vary
about :.. Ti.. ... erature of lake water is generally less than
the temperature of air during the day and greater than the
temperature of air during the night. For a day, or for periods of a
few days, the mean temperatures of lake water and air may differ by
several degrees, especially at times of rapid change in weather, but
for shallow lakes the monthly mean temperatures of the surface
water and the local air seldom differ by more than 4 I. Thus, for
conceptual purposes, the mean-monthly temperature of air at
Panama City, shown in figure 5, is fairly representative of the
mean-monthly temperature of the surface water of Deer Point Lake.
This is partly confirmed by results of intermittent measurements of
the temperature of Deer Point Lake water made since 1966 which, as
figure 5 shows, generally follow the trend of the mean-monthly
temperature of air at Panama City.
At times the temperature of the lake water varies appreciably with
depth-the temperature generally decreasing from the surface to the
bottom. The temperature gradient develops because heating by the
sun occurs in the uppermost layers of lake water and because, above
a temperature of 39 F, the density of water decreases with increasing
temperature. Thus, water heated at the surface tends to remain at the
surface. The difference between the temperatures of surface water
and bottom water can build up to several degrees. However, other
factors that come into play tend to restore the lake water to uniform
temperature.
First, cooling of the lake water also occurs at the surface by
radiation, conduction, and evaporation. The cooled water sinks
below the surface to blend with water of equal density. Currents so
induced reduce the thermal gradient, but these currents probably are
not strong enough to eliminate the gradient entirely.
Second, and undoubtedly more important, the wind induces
currents in the lake water that are powerful enough to mix the water
to great depths, the depth depending on the intensity and duration
of the wind as well as on the size and shape of the lake basin and the
degree of its exposure to the wind.
Because the open-water areas of Deer Point Lake are shallow and
open to the wind, the lake water is probably mixed completely by
moderate winds. Thus, from top to bottom, the temperature of
water in Deer Point Lake is relatively uniform except at times when
the wind is calm for periods of several hours on warm and sunny
days.
REFERENCES
Barnes, H. H.. Jr. (and Golden, H. B.)
1966 Magnitude and frequency of floods in the United
States, Part 2-B, South Atlantic slope and eastern
Gulf of Mexico basins, Ogeechee River to Pearl River.
U. S. Geol. Survey Water Supply Paper 1674, 409 p.
Florida State Board of Conservation
1954 Summary of observed rainfalls on Florida to 31
December 1 952 Florida State Board of
Conservation, Division of Water Survey and Research
Paper No. 11, 334 p.
Hem, J. D.
1959 Study and interpretation of the chemical
characteristics of natural water U. S. Geol. Survey
Water Supply Paper 1473, 269 p.
Musgrove, R. H. (and Foster, J. B. and Toler, L. G.)
1965 Water resources of the Econfina Creek basin area in
northwestern Florida. Florida State Board of
Conservation, Division of Geology, Rept. of Inv. 41,
51 p.
1968 Water resources records of the Econfina Creek basin
area, Florida' Florida State Board of Conservation,
Division of Geology, Information Cirec. No. 57, 127 p.
Pride R. W. (and Crooks, J. W.)
1962 The drought of 1954-56, its effect on Florida's
surface-water resources IFlorida State Board of
Conservation, Division of Geology, Rept. of Inv. No.
26, 65 p.
U. S. Geological Survey
1963-66 Water resources data for Florida, part 1, surface water
records, vol. 3, lakes: U. S. Geol. Survey, Tallahassee,
Fla., issued annually.
1963 Water resources data for Florida, part 1, surface waier
records, vol. 1, streams, northern and central Florida.
U. S. Geol. Survey, Tallahassee, Fla., issued annually.
1951 Surface water supply of the United States, 1948, part
2, South Atlantic slope and eastern Gulf of Mexico
basins: U. S. Geol. Survey, Water Supply Paper 1112,
554 p.
U. S. Public Health Service
1962 Drinking water standards: U. S. Dept. of Health,
Education, and Welfare, Public Health Service
Publication No. 956.
U. S. Weather Bureau
1954-69 Climatological data, Florida, Annual Summaries
1953-68: U. S. Dept. Commerce, E. S. S. A.,
Asheville, N. C.

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES
TALLAHASSEE, FLORIDA
1970